1. Field of the Invention
This invention relates to a control device for controlling the action of a movable optical member in an optical apparatus.
2. Description of the Related Art
The power zoom lens barrels of conventional video cameras or the like have been arranged to vary a focal length by driving a zoom motor, according to an input signal from a zooming operation part, to rotate a cam ring or the like restricting the movement of a lens which is movable in the direction of an optical axis. The variations of the focal length have been dependent on the shape of a cam groove formed in the cam ring.
To solve this problem, it has been proposed to cause the focal length to vary at a constant rate relative to zooming time by rectilinearly forming the cam groove, for example, as disclosed in Japanese Patent Application Laid-Open No. SHO 63-167335.
It has also been proposed, as disclosed in Japanese Patent Application Laid-Open No. HEI 3-200127, to cause a driving voltage to increase on the side of wide-angle positions of a zoom lens and to decrease on the side of telephoto positions, according to the zoom position of the zoom lens. It has been further proposed, as disclosed in Japanese Patent Application Laid-Open No. HEI 1-161325, to vary the focusing lens driving speed according to the operating speed of operation means.
Further, it has been also proposed in Japanese Patent Application Laid-Open No. SHO 61-196214 to vary the rate of driving amount of a stepping motor used for driving the lens according to information on the aperture value and the focal length.
Meanwhile, various devices for detecting the rotation of a manual operation member which is to be rotatively operated and for driving an optical system with a motor have heretofore been proposed. These devices include the following:
A power focusing device disclosed in U.S. Pat. No. 4,864,344 is arranged to count a signal input to a manual operation member as pulses per rotation angle, to have an encoder at a motor provided for moving a focusing member of the optical system and to drive the motor as much as the amount of the above-stated count or in proportion to the amount of the count according to the output of the encoder of the motor.
A power focusing device disclosed in Japanese Patent Application Laid-Open No. HEI 1-161325 is arranged to detect the amount and speed of rotation of a manual operation member and to change the amount of driving a motor on the basis of the values thus detected.
A power focusing device disclosed in Japanese Patent Application Laid-Open No. HEI 1-182812 is arranged to detect the rotation speed of a manual operation member and to selectively set the high or low level of a motor driving output on the basis of the value detected.
Further, in a case where an input keyboard is used for a computer, a system contrived to prevent a process from being unable to follow an input from the keyboard is widely in use. For this purpose, the system is arranged to permit a prior input with data stored at a ring buffer by allowing an interruption when the keyboard is pressed.
The lens barrel of the kind having a cam groove formed in a cam tube in a rectilinear shape for the purpose of making the focal length varying rate constant, however, has presented the following problems: it is inferior in optical performance and also makes designing work more difficult than the conventional lens barrel of the kind having no limitation in the cam groove shape.
In the case of the proposed arrangement to vary driving control according to lens information, the control is arranged to be performed without taking the operating speed of the operation part into consideration. It, therefore, brings about a feeling of discrepancy between an operation intended by the photographer and an actual lens driving operation.
In the case of an ordinary zoom lens, on the other hand, the zooming operation feeling of the photographer varies according to the object distance as the focal length varies with the object distance.
Further, there has been disclosed no method of controlling lens positions using parameters other than the operating speed of the operation part, such as the amount of operation, the focal length and the object distance.
Further, in the case of the conventional device arranged to detect the rotation of the manual operation member to be rotatively operated and to drive the optical system with a motor, no heed is given to a time difference between the input timing of the manual operation member and the timing of completion of actual motor driving. As a result, there have been the following problems:
(i) When an instruction signal for a new action is inputted from the manual operation member before completion of a motor driving action in response to a previous instruction signal, a shift is made to a sequence of processes for the new action before completion of the previous action. The premature shift tends to cause an unstable operation. PA1 (ii) With an instruction signal for a new action inputted from the manual operation member before completion of the motor driving action in response to the previous instruction signal, the premature shift to the sequence of processes for the new action also hinders an adequate operation pattern tracing action.
The ring buffer which is conventionally used for the keyboard of a computer is arranged to handle data which has established meaning at the time of input. However, no arrangement has been known for processing information of a time serial input such as the intervals of input from the manual operation member by storing it at the ring buffer. Besides, the ring buffer necessitates use of a plurality of keys in a case where it is desired to designate information of a plurality of kinds.